This invention relates to a multilayer polymeric composite in which a polymeric surface layer is chemically bonded to a cross-linked, isocyanate-modified thermosetting unsaturated polyester or polyether resin layer to provide a high impact strength, delamination-resistant structure.
U.S. Pat. No. 4,664,982 describes a composite structure, e.g., a reinforced enameled steel product, having high impact strength and thermal shock resistance. The composite structure is formed having bonded thereto a finish layer on one side thereof and on the other side a layer of reinforced plastic to provide a laminate. While the composite structure possesses generally excellent physical and mechanical properties as a result of the chemical bonding, or union, of the reinforced plastic layer to the enameled steel layer, due to the presence of steel, the structure is fairly heavy for a given level of strength and stiffness. Other disclosures of the chemical bonding of an organic polymeric material to an inorganic material such as metal, glass or ceramic can be found in U.S. Pat. Nos. 3,477,869; 3,661,628; 3,671,562; 3,705,911; 3,706,592; 3,754,971; 3,956,353; 4,147,712; and, 4,156,677, among others.
Numerous unsaturated polyesters and polyethers including those modified by reaction with isocyanates, and cross-linked dense foams prepared therefrom are known in the art.
Borgnaes et al. (Ashland Chemical Company), "RIMing of Low Viscosity Crosslinkable Alcohols with Diisocyanates", a paper presented at a meeting of the Polyurethane Manufacturer's Association in Miami, Fla. on Oct. 18, 1983, describes the chemistry of a commercially available unsaturated monoalcohol ester monomer, Ashland Chemical Company's V110-2, and the aromatic diisocyanate adduct of the ester. This monomer and its aromatic diisocyanate adduct are among the useful polyester materials which can be used in whole or in part to provide the polymeric composite of the present invention. A generic disclosure of the unsaturated monoalcohol ester monomer may be found in U.S. Pat. No. 3,663,599. Ashland Chemical Company's polyester and its use in the reaction injection molding (RIM) of fiber-reinforced composite structures are discussed in its product information brochures ASHLAND V110-2, ARIMAX 1000 SERIES RESINS and ARIMAX 1000 SYSTEM. Amoco Chemicals Corporation's Technical Service Report Nos. GTSR 18 ("Updated Hybrid Resin Technology"), GTSR 26 ("Aromatic Mixed Esters For Urethane Applications"), GTSR 27 ("Polyester Polyols for Reaction Injection Molding") and GTSR 32 ("Aromatic Polyester Thermoplastic Urethanes Program Summary") describe another type of isocyanate-modified polyester which can be used in the manufacture of the polymeric composite structure herein.
U.S. Pat. No. 3,367,992 describes thermosetting foams based on ester monomers which, like Ashland Chemical Company's V110-2 ester monomer, contain both terminal hydroxyl functionality (as part of a carboxylic acid group) and terminal ethylenic unsaturation. Adducts of the ester monomers with a polyfunctional material such as a polyisocyanate are also described. Other disclosures of thermosetting unsaturated polyesters and/or their polyisocyanate adducts can be found in U.S. Pat. Nos. 3,772,241; 3,823,099; 3,883,612; 4,119,510; 4,216,294; Reissue No. 31,468 (of 4,256,910); 4,280,979; 4,314,036; 4,358,548; and, 4,464,320. For still other useful polyester materials, reference may be made to "Polyesters, Unsaturated" in the Encyclopedia of Polymer Science and Technology, Vol. 11, pp. 129 et seq., Bjorkstein et al., Polyesters and Their Applications, 4th ed., Reinhold Publishing Company, New York (1960) and Boeing, Unsaturated Polyesters: Structures and Properties, Elsevier Publishing Company, Amsterdam (1964). U.S. Pat. Nos. 3,654,224 and 3,917,666, among others, describe unsaturated polyethers which are useful in the practice of the present invention.
Multilayer polymeric composites in which a polymeric layer or coating is associated with a thermosetting polymer substrate are known. U.S. Pat. No. 3,257,266 describes a fiber-reinforced unsaturated polyester foam structure possessing a weatherable polyvinyl fluoride facing. U.S. Pat. No. 4,053,545 describes a laminated structural foam possessing an injection molded thermoplastic fiber-reinforced dense foam backing, e.g., one of polyethylene or polystyrene, adhesively bonded to a thermoformed finish layer, e.g., one of acrylic such as Swedcast cast acrylic sheet type 300. The laminated foam is said to be useful in the manufacture of wash basins, shower stalls, bathtubs, etc. U.S. Pat. No. 4,130,614 describes a structural laminate possessing a fiber-reinforced polyesterurethane foam backing layer and a facing sheet such as paper, acrylic film and polyvinylfluoride film. U.S. Pat. No. 4,315,964 describes a laminate possessing a cured layer of glass fiber-reinforced unsaturated polyester and a surface layer of polyvinyl fluoride film. RIM is one of several processing techniques which can be used to manufacture the laminate. U.S. Pat. No. 4,551,390 describes the molding of multi-ply polymeric composites employing thick molding compounds (TMC), bulk molding compounds (BMC) or sheet molding compounds (SMC) and unsaturated ester monomers such as those disclosed in U.S. Pat. Nos. 3,772,241 and 3,883,612, supra.
While none of the foregoing prior patents discloses or suggests the chemical bonding of a polymeric layer or coating to a thermosetting polymer substrate, the chemical bonding of dissimilar organic polymers is known. According to U.S. Pat. No. 3,501,564, a non-cured polyurethane elastomer layer and a different non-cured polymer surface layer are simultaneously cured to provide permanent unification or cross-linking or chemical and mechanical integration thereof. The non-cured surface polymer can be an epoxy resin which has been applied to a mold surface and cured only to the point of being self-sustaining. The heat produced by the curing polyurethane layer will effect the curing of the epoxy surface layer and also result in the bonding of the two layers as previously described. U.S. Pat. Nos. 3,507,114; 3,716,604; 3,813,308; 4,053,680; and, 4,232,608 describe the chemical cross-linking of the polymer matrix component of a solid rocket propellant with the polymeric component of the rocker motor casing, or liner. U.S. Pat. No. 3,507,114 employs a diisocyanate to react with the hydroxyl groups of a hydroxyl-terminated polybutadiene, the polymer which is common to both the propellant matrix and the liner. Similar approaches to chemical bonding are disclosed in aforementioned U.S. Pat. Nos. 3,716,604, 3,813,308 and 4,232,608 as well as in U.S. Pat. No. 4,337,111. U.S. Pat. No. 3,725,174 describes the chemical bonding of at least two layers of normally incompatible polymers, e.g., a highly hydrogen-bonded polymer such as cellulose and a thermoplastic polymer such as polyethylene, employing an ethylenically unsaturated carboxylic acid or anhydride such as maleic anhydride and a free radical initiator. U.S. Pat. No. 3,764,370 achieves chemical cross-linking of a resin substrate to a resin coating by generating "living" radicals at the surface of the resin substrate employing ultraviolet light radiation, the "living radicals" then reacting with suitable groups possessed by the resin coating. U.S. Pat. No. 3,959,521 describes chemically uniting a resinous topcoat to a polymeric base by applying to the latter an undercoat based on a composition containing both ethylenically unsaturated groups and free isocyanate groups, applying the topcoat which also contains ethylenically unsaturated groups and curing both the undercoat and the topcoat. U.S. Pat. No. 4,282,285 describes a RIM process for making automobile bumper fascia in which a liquid microcellular polyurethane reacting mixture is polymerized against a decorative or protective transfer coating containing a polyurethane catalyst. The catalyst acts to bond the transfer coating to the polyurethane so that the shaped part upon removal from the mold contains a firmly adherent coating of the transfer coating composition. The transfer coating can be either a thermoplastic or a thermosetting polymer, with or without a plasticizer. Examples of useful transfer coatings include acrylic and acrylic ester polymers, pre-reacted urethane polymers, saturated and unsaturated polyesters, epoxy esters, cellulose esters, polyolefins, and vinyl an vinyl-melamine polymers. U.S. Pat. Nos. 4,333,987, 4,337,296 and 4,361,626 describe related procedures for chemically bonding dissimilar polymeric materials, e.g., a vinyl resin material and a polyurethane, to provide multi-layer sheet materials such as resilient floor, wall or ceiling coverings, or resilient desk, table or counter tops.
None of the foregoing prior patents relating to the chemical bonding of dissimilar polymeric materials even remotely suggests the application of chemical bonding to the manufacture of a composite, or laminate, possessing a polymeric cosmetic layer and a cross-linked, isocyanate-modified, thermosetting polyester or polyether resin substrate layer as in the present invention.
It is an object of the present invention to provide a multilayer polymeric composite which is significantly lighter than a metal-containing, e.g., steel-containing, polymeric composite for an approximately equivalent level of strength and stiffness.
It is another object of the present invention to provide a multilayer polymer composite which is exceptionally resistant to delamination due to the chemical bonding of dissimilar polymer layers.
It is yet another object of the present invention to provide a multilayer polymeric composite which readily lends itself to manufacture by RIM or RRIM technology.